How hot is too hot? As extreme heat waves sweep across Europe, experts reveal the upper temperature limit for human safety, and it’s much lower than we thought.
- The limit had been thought to be 95°F with 100% humidity.
- But new research suggests it’s actually 87°F (31°C) with 100% humidity
It may be warm in Britain, but the rest of Europe has been roasting in record heat in recent days.
And it’s not just on the mainland where millions of people have been sweltering in temperatures well above “normal”: the mercury also topped 122°F (50°C) in parts of the US and China earlier this week.
It has raised concerns not only for the elderly, the young, or those with health conditions, but also for the impact this unprecedented heat will have on healthy young adults as global warming continues to wreak havoc.
So how hot is too hot?
Well, experts have revealed the upper temperature limit for human safety, and it’s actually much lower than we thought.
Warning: Experts have revealed the upper temperature limit for human safety, and it’s actually much lower than we thought. It occurs when extreme heat waves sweep across Europe. Pictured is a woman fanning herself from the heat and roasting conditions in Rome this week.
Analysis: Calculated based on the combination of heat and humidity, known as the ‘wet bulb temperature’. This graph shows the point where temperature and relative humidity together become dangerous for the human body (the red area).
WHAT IS WET BULB TEMPERATURE?
‘Wet bulb temperature’ (TW) is measured by placing a damp cloth on the bulb of a thermometer.
It is altered according to the actual temperature and humidity, but if the TW exceeds 103°F, the body can no longer cool itself.
This is defined as “dangerous” by the US National Weather Service and if it reaches 124°F or higher, it poses extreme danger.
The heat and humidity that cause a ‘wet bulb temperature’ of this enormity can lead to heat stroke which in turn can trigger damage to the brain, heart, kidneys and muscles.
At an actual temperature of just 90°F, if the humidity climbs to 95 percent, it can hit the 124°TW threshold for ‘extreme danger.’
However, if the humidity remains low, say around 45 percent, the actual temperature would have to climb as high as 104°F before reaching the “extreme danger” limit.
The so-called ‘wet bulb temperature’, which takes humidity into account, of just 35°C can be fatal after just a few hours, even for the fittest person.
The key point to keep in mind is that it’s not just about what the thermometer says.
Instead, it is the combination of heat and humidity, known as the ‘wet bulb temperature’.
This is measured by placing a damp cloth on the bulb of a thermometer.
It is a direct indicator of how well sweating cools the body.
A wet bulb temperature of 95°F (35°C), equivalent to 95°F with 100% humidity, or 115°F with 50% humidity, was previously thought to be the safe upper limit for humans.
At this point, the human body would no longer be able to cool itself by evaporating sweat from the body’s surface to ensure a stable core body temperature.
However, new research now suggests that the upper limit is actually 87°F (31°C) at 100% humidity or 100°F (38°C) at 60% humidity.
The study, which was conducted by experts at Pennsylvania State University, saw healthy men and women subjected to heat stress in a controlled environmental chamber.
Each person was given a small telemetry pill to swallow so that their core temperature could be monitored as they slowly moved about doing everyday activities like eating, cooking and showering.
As they did so, the researchers increased the heat or humidity in the chamber to see at what point each participant’s core temperature began to rise toward what is known as the “critical environmental limit.”
This is where there is suddenly a higher risk of heat-related illness.
Europe is enduring what could end up being the hottest week in its history. Here, people cool off in the Trevi Fountain in Rome as a heat wave sweeps through Italy.
WHAT IS HEAT STROKE?
Heat stroke is when the body can no longer cool itself and a person’s body temperature becomes dangerously high due to prolonged exposure to direct sunlight.
Common symptoms include:
- Confusion, altered mental status, slurred speech
- Not sweating – a sign of being dehydrated
- Loss of consciousness, incoherence
- Hot, dry skin or profuse sweating
- Nausea or vomiting
- very high body temperature
- Dizziness or headache
- fast and strong pulse
The reason for this is that the heart has to work harder to pump blood to the skin to help dissipate heat, while sweating decreases the fluids in your body.
As the body continues to overheat, it can even lead to heat stroke.
This is a serious and life-threatening condition that requires immediate medical treatment to cool the body.
It can damage organs such as the lungs, kidneys, and liver. If left untreated, it can be fatal.
Heat stroke can occur during heat waves or prolonged periods of very hot weather.
Some people, such as children, the elderly, and those with long-term health problems (such as diabetes or heart problems), are at higher risk of heat exhaustion or heat stroke.
As a result, they have to be very careful in hot weather.
Following up on their latest research, the experts now want to test older men and women to see what their safe upper limit is.
Because of your increased risk of heart disease and respiratory problems, it’s likely to be much lower.
Such information is important because, as the world’s average temperature continues to rise and heat waves become stronger and more intense, the impact this will have on human health remains to be seen.
THE PARIS AGREEMENT: A GLOBAL AGREEMENT TO LIMIT TEMPERATURE RISE THROUGH CARBON REDUCTION TARGETS
The Paris Agreement, which was first signed in 2015, is an international agreement to control and limit climate change.
He hopes to keep the global average temperature rise below 2°C (3.6°F) ‘and continue efforts to limit the temperature rise to 1.5 °C (2.7 °F)’.
It seems that the more ambitious goal of restricting global warming to 1.5°C (2.7°F) may be more important than ever, based on previous research that says 25% of the world could see a significant increase in drier conditions.
The Paris Agreement on Climate Change has four main objectives with regard to reducing emissions:
1) A long-term goal of keeping the global average temperature rise to well below 2°C above pre-industrial levels
2) Seek to limit the increase to 1.5°C, as this would significantly reduce the risks and impacts of climate change
3) Governments agreed on the need for global emissions to peak as soon as possible, recognizing that this will take longer for developing countries.
4) Undertake rapid reductions thereafter based on the best available science